Reestablishment of blood flow within 5 hours of coronary artery occlusion has been associated with increased survival of myocardium. However, since myocardial muscle is irreversibly damaged before blood vessel networks are destroyed, normal flow may resume without associated myocardial salvage. In 7 dogs with closed chest coronary artery occlusion, release of the occlusion after 5 hrs produced normal blood flow in areas that three days later were shown to be necrotic. Normal blood flow in reperfused myocardium does not indicate myocardial viability.